Laser diode driving systems and methods

Abstract

A laser diode driving method that reliably maintains average optical power and extinction ratio is disclosed. The present invention for laser driving uses a preloaded laser diode characteristic curve/table and/or mathematical equations to create a programmable bias and modulation current range. This ensures stable closed-loop operation and prevents system failure if the feedback signal is impaired by confining the operation of the laser diode to a normal operating range.

What is claimed is: 
     
       1. A laser diode driving system, comprising:
 a laser diode driver that generates an output current that drives a laser diode; 
 a look-up table comprising 
 a bounded safety range for a bias of the output current and a bounded safety range for a modulation of the output current; 
 a feedback bias and modulation comparator that receives data on a laser diode output of the laser diode and that outputs a command setting to alter at least one of the bias and the modulation of the output current as a function of the received data to maintain a target and an extinction ratio between P 1  and P 0 ; 
 a control mechanism that applies the command setting to the laser diode driver when the command does not exceed either the bounded safety range for the bias of the output current or the bounded safety range for the modulation of the output current. 
 
     
     
       2. The laser diode driving system of  claim 1 , wherein the target comprises a user-defined average target for the data on the laser diode output, wherein the feedback bias and modulation comparator outputs the command setting to alter the output as a function of both the received data and the user-defined average target. 
     
     
       3. The laser diode driving system of  claim 1 , further comprising a photo detector disposed to receive the laser diode output and generate the data, which is transmitted to the feedback bias and modulation comparator. 
     
     
       4. The laser diode driving system of  claim 3 , further comprising a trans-impedance amplifier that amplifies a signal received from the photo detector, wherein the photo detector transmits data to the feedback bias and modulation comparator via the trans-impedance amplifier. 
     
     
       5. The laser diode driving system of  claim 1 , further comprising a preload laser diode driver that defines the bounded safety range for the bias of the output current or the bounded safety range for the modulation of the output current. 
     
     
       6. The laser diode driving system of  claim 1 , wherein the look-up table further defines temperature-specific settings for driving the laser diode. 
     
     
       7. The laser diode driving system of  claim 6 , further comprising programmable range settings for each temperature-specific setting of the look-up table, wherein the control mechanism limits the application of the recommendation to the laser diode driver as a function of the programmable range settings. 
     
     
       8. The laser diode driving system of  claim 1 , wherein the target is user-selected from a high power target, a low power target, and a user-defined average target for the data on the laser diode output, wherein the feedback bias and modulation comparator generates the recommendation as a function of both the received data and a selected one of the average target, high power target, and low power target. 
     
     
       9. The laser diode driving system of  claim 8 , further comprising a preset user interface that sets the high power target, the low power target, and the average target. 
     
     
       10. The laser diode driving system of  claim 8 , further comprising a preset user interface that sets the average target, and a power level target optimizer that determines the high power target and the low power target as functions of the average target. 
     
     
       11. A method for driving a laser diode, comprising:
 defining a bounded safety range for a bias of an output current to the laser diode; 
 defining a bounded safety range for a modulation of the output current to the laser diode; 
 generating the output current to the laser diode; 
 receiving data on an output laser from the laser diode; 
 outputting a command setting to alter at least one of the bias and the modulation of the output current as a function of the received data to maintain an extinction ratio between P 1  and P 0 ; 
 applying the recommendation to alter the output current when the command setting does not exceed either the bounded safety range for the bias of the output current or the bounded safety range for the modulation of the output current. 
 
     
     
       12. The method of  claim 11 , further comprising triggering a warning when the recommendation violates either the bounded safety range for the bias of the output current or the bounded safety range for the modulation of the output current. 
     
     
       13. The method of  claim 11 , further comprising:
 receiving the laser diode output via a photo detector; and 
 generating the data on the output laser via the photo detector. 
 
     
     
       14. The method of  claim 11 , further comprising amplifying the generated data using a trans-impedance amplifier. 
     
     
       15. The method of  claim 11 , further comprising defining the bounded safety range for the bias of the output current and the bounded safety range for the modulation of the output current using a preload laser diode driver. 
     
     
       16. A laser diode driving system, comprising:
 a laser diode driver that generates an output current that drives a laser diode; 
 a look-up table comprising a bounded safety range for a bias of the output current, a bounded safety range for a modulation of the output current, a user-defined average target, a high target, and a low target; 
 a user interface that receives a selection of one of the high target, the low target, and both the user-defined average target for the data on the laser diode output; 
 a feedback bias and modulation comparator that receives data on a laser diode output of the laser diode and that outputs a command setting to alter at least one of the bias and the modulation of the output current as a function of the received data and the selection to maintain a user-defined extinction ratio between P 1  and P 0 ; and 
 a control mechanism that applies the command setting to the laser diode driver when the command does not exceed either the bounded safety range for the bias of the output current or the bounded safety range for the modulation of the output current. 
 
     
     
       17. The laser diode driving system of  claim 16 , wherein the high target and low target are automatically generated as a function of the user-defined average target. 
     
     
       18. The laser diode driving system of  claim 17 , wherein the function is user-defined.